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An ocean is defined as a continuous body of saline water. There are 5 major oceans the Arctic Ocean, the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Southern Ocean. Approximately 71 % of the Earth’s surface in covered by ocean. When asked about the color of the ocean most people respond that that it is blue, aqua or green. The ocean however is actually none of these colors, so what makes the ocean appear blue? This article will answer that question.

A basic understanding of color
To understand why we perceive the ocean to be blue, we must first understand how our eyes see color. If you have ever refracted light through a crystal, you know that white or clear light is made up of many colors. Different wavelengths of light, red, yellow, green and blue, are reflected back into our eye and enable us to see certain colors. When we see a particular color this is because the other wavelengths are either reflected to a lesser extent or absorbed by the material reflecting them. So when light hits a green plant, for example, we see the plant as green because the plant reflects back the green wavelength of light more than the others.

Why is the ocean blue?
So why is the ocean blue? It all starts when light, such and sunlight, hits the water in the ocean. The ocean filters the light and absorbs the red, yellow and, to some extent, green wavelengths of light. It reflects back the blue wavelength of light and our eyes perceive the ocean as blue. The deeper the water the deeper blue it will appear as it will reflect more of the blue light and less of the other colors. You will also see less reflection off the ocean’s surface. Shallower water will reflect back some green light making the water appear more turquoise or aqua in color. When oceans appear particularly green this is often because there is other material such as plant life that reflect back a different wavelength of light (such as yellow). The two wavelength of light combine and our eyes perceive the ocean to be green.

When the ocean is particularly calm the particles in the water make the ocean act in the same manner as a mirror. The ocean will reflect the color of the sky in these incidences and that is why the ocean can appear to be red at sunset. However, the water is not actually this color.

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